Cathode-ray oscillograph



March-31, 1953 E RUSKA ETAL 2,633,553

cATHoDE-RAY oscILLoGRAPH Filed Jan. 51, 1951 Inl/enfans Patented Mar. 31, 1953 UNITED STATES PATENT OFFICE CATHODE-RAY OSCILLOGRAPH German corporation Application January 31, 1951, Serial No. 208,766 In Germany November 26, 1948 6 Claims.

This invention is concerned with a cathoderay oscillograph.

It is customary in cathode-ray oscillographs to use for the focusing of the electron beam electronic lenses which are disposed in the beam path between the beam generator and the beam deflection plates. The lenses employed for this purpose may be of the electrostatic or of the electromagnetic type.

In accordance with the invention, there is provided between the beam generator and the deflection plates an electronic lens system comprising two electrostatic lenses, namely, a first electrostatic lens having a short focal range for producing a reduced image of the cathode spot, and a second electrostatic lens forming ahead of the deiiection plates an immersion lens which utilizes said reduced cathode spot as a source of electrons for focusing the beam. The iirstnoted lens comprises two outer electrodes lying on the same potential and a second electrode lying on a diiierent potential. The immersion or focusing lens is formed by the anode and an associated electrode.

The reduced image of the cathode spot is produced by the first-noted lens ahead of the immersion or focusing lens, thus furnishing a Darticularly small and ne electron source spot for the electron beam, making it possible to focus the tracing point upon the viewing screen as a very fine, sharply defined point.

In accordance with another object of the invention, the central electrode of the individual electrostatic lens is placed at the cathode potential, while its two outer electrodes are placed at a potential lying between the cathode and the anode, preferably approximately at half of the anode voltage.

This latter feature permits the following structural embodiment of the lens system which may` be mentioned by way of example: A first acceleration system for the electrons is formed by the Wehnelt-cylinder of the beam generator and an electrode placed at half of the anode voltage. In the path of the beam serially succeeding this first acceleration system is disposed the first lens which reduces the size of the cathode spot. A second acceleration system is formed by the immersion or focusing lens disposed serially with respect to the rst lens but ahead of the deflection plates. An electrode of said second acceleration system is disposed ahead of the anode and is placed at half of the anode voltage.

The subdivision of the anode voltage provides .for an electrically safe structure which is of importance. e. g., in applying the invention in the case of heavy-duty cathode ray oscillographs operating with an anode voltage amounting, for example, to 25 kv., so as to obtain high tracing speed.

A further object of the invention is to provide a structurally particularly simple arrangement 0f the various electrodes of the lens system by the use of two metallic cylinders carrying half of the anode voltage. These cylinders have preferably semi-spherical ends forming apertures for the passage of the beam, serving as electrodes. one of said cylinders forming electrodes coacting respectively with the Wehnelt-cylinder and the central electrode of the first lens, and the other cylinder forming electrodes respectively coacting with the central electrode of the first lens and with an electrode of the second lens.

The above-mentioned metallic cylinders are provided with axially spaced circular mounting disks which are supported in insulated relationship by ceramic members disposed inside the tube. It is advantageous, for the purpose of increasing the creepage or leakage path, to support by means 0f separate ceramic tubing the mounting disk facing the Wehnelt-cylinder and the mounting disk facing the anode. These separate ceramic tubing members may be supported by insulating members extending from the other mounting disk.

The objects indicated above and additional objects and features will become apparent from a description of an embodiment of the invention which will presently be rendered with reference to the accompanying drawings. In these drawings, Fig. 1 shows a heavy duty cathode-ray oscillograph in diagrammatic longitudinal sectional view; and

Fig. 2 represents a diagrammatic transverse section taken approximately along lines A, B of Fig. 1.

The beam generator comprises the glow cathode l and the Wehnelt-cylinder 2. Numeral 3 indicates the anode. As shown, the anode is disposed directly facing a first pair of deflection plates 4 to which is connected the voltage to be measured. Numeral 5 designates an intermediate shield carrying marginal angles at both sides. successively in the path of the beam is disposed the second pair of deiiection plates B and a terminal shield T which is likewise provided with marginal angles.

Two metal cylinders 8 and il are built into the tube to form the lens system. The opposite electrodes I3 and lI5 tion system.

pending on a time factor. vplates are for this purpose connected with the ends of these cylinders are semi-spherical and are provided with apertures for the passage of the beam. These cylinders form in this manner the semi-spherical electrodes 9-IIl and I2--i3, respectively. At I4 is indicated the central electrode of the individual lens, referred to before as the rst lens, which has, in accordance with the invention, a short focal range to reduce the size of the cathode spot. The electrodes I` and I2 form the coacting outer electrodes of this lens. The anode 3 on its upper side likewise carries a semi-spherical terminal electrode mem-` ber I5 which faces the electrode I3.

The above described electrodes form a first acceleration system for the electrons comprising the Wehnelt-cylinder 2 and the electrode .9.,

vuseful in cathode-ray tubes aside from the specinc use thereof in an oscillograph, and it is understood, therefore, that the disclosure should be given corresponding latitude.

Changes may be made within the scope and A spirit of the accompanying claims.

We claim: l. In a cathode-ray oscillograph having beamgenerating and beam-deflecting means, a pair of which is placed on one-half of the anode volt-' age. In series relationship thereto is the indiserially related electrostatic lenses disposed between said beam-generating and deflecting means, one of said lenses forming an immersion lens 'comprising an anode and a coacting vdual cathode spot reduction lens comprising the electrodes I0, I4 and I2. Serally related thereto, vwithin-the path of the beam, is 'disposed the-immersion 0r focusing lens comprising the formi-ng ra i second .accelera- 'I'he various electrodes are secured by means of circular disks .I-23, inclusive, which are in turn mounted by means of ceramic members 24. Associated with the .cylinders 8, to obtain proper centering thereof, is the disk I8. .The cylinder Il is held in a similar manner by the disk 2l and the `disk 22.

in order to increase the Yleakage or creepag path, the disks i8 and 22 are separately Vsupported by ceramic members '26 which are in turn f secured tothe mounting disks I3 and 2l.

'The conductor 5t, which connects the disks -or .plates 'l5 and 2l .is carried through a separate f opening '5I inthe disk 2E). The parts so far described are 4built-into the 'envelope ofthe tube 2 which carries a viewing screen '23 at its .lower end. The electrical conductorsare carried in a kvacuum-tight manner 'through the upper tube wall 29 and through the laterally disposed inlets Bt, 3|, 32, respectively.

. A voltage divider 33 maybe provided, as shown,

to' supply 'the various potentials. The heating -current for the cathode may be supplied from ythe battery 34 or from a suitable commercial ...for the .central electrode --I4 Vof the individual Vcathode spot-reducing lens. The cylinders 8 and 'ii .are connectedto onehalf .of the anode voltage over .the conductor ,3-5.

The anode 3 is connected to the voltage divider l l ever-.the line '68. The intermediate shield ,5 Aand .the terminal shutter 'i' are at the samepotcntial over the conductors lil-L32. The commercial I .current source is connected at 44, and,A the iirst pair ofdeiiection plates Il is connected with such source over the conductors 65, 46. Numeral 41 indicates a device provided for deflection, de-

The two Ydeflection device 4l over the vlines 48-439.

The electrodes 2 and 9 accelerate the electrons to one-half of the anode potential. `The lens ID, I4, I2 forms the cathode .spotin front -of .the immersion lens I3, l5, on a vreduced scale, andthe- 424-4-3 are associated with common .supports 8 electrode disposed in the beam path ahead of said deiiecting means for focusing said beam,

. said other lens being disposed ,inthe beam-path ahead of said immersion lens and havinga-.short focal range to produce a .reduced image 1of vthe cathode spot which serves as an electronsource for said immersion lens. y y

A2. The structure defined in claim l, wherein saidA seccndnoted lens comprises a central electrode two outer coacting electrodes, means for placing said central electrode at 'cathode petential, and means for placingpsaid two outer electrodes at one-half of the anode potential.

5. The structure dei-ined ,in claim l, wherein vsaid beam-generating means comprises -a Wehneit-cylinder, a coacting electrode forming with v'said Wehnelt-cylinder a first electron acceleration system, meansfor placing said coactingg electrode on ene-half of t-ne anode voltage, said ,sec-

Y ond-noted lens being disposed in serial relationship with said rstpacceleration system, said immersion lens forming a second electrona'cceleration system and comprising an electrode which is Adisposed ahead of the anode and is placed at lonehalf of the anode voltage.

4. The structure dei-ined in claim 1 wherein said beam-generating means comprises a Wehnelt-cylinder, a pair of metal cylinders, means for placing said cylinders on one-half of the anode voltagasaid cylinders having apertured ends formed `in semi-spherical sha-pe, the ends of one of said cylinders forming enacting electrodes for said Wehnelt-cylinder and for an 'elec- V trode which forms the centralelectrode -of said Vsecond-noted lens, .respectivelyJ and the ends of .said other cylinder forming electrodes v'for o oaction with said central electrodeof said ,second-noted Alens and thel anode, respectively. A

5. The structure defined in cla-im 1, wherein said beam-generating means comprises a Wejhnelt-cylinder, a pair of coaxially serially disposed metal cylinders forming electrodes for coaction with said Wehnelt-cylinder and with an Ielectrede which forms the central electrode of said second-noted lens and for coaction with said central electrode `and the anode, respectively, means for securing said metal cylinders each .at a plurality cf axially spaced vpoints comprising circular mounting disks, and means for separately securing the ends of said disks which face said Wehnelt-cylinder and said anode, respectively. y 6. A cathode-ray oscillograph comprising beam-generating means having a cathode, aplurality of electrodes disposed serially in succession in the path of the beam produced by said y beam-generating means, said electrodes compris- 6 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,227,016 Schlesinger Dec. 31, 1940 2,228,958 Insch Jan. 14, 1941 2,429,824 Koch et al Oct. 28, 1947 2,432,037 OLal'te et al Dec. 2, 1947 2,454,345 Rudenberg Nov. 23, 1948 2,476,066 Moss July 12, 1949 2,484,721 Moss Oct. 11, 1949 2,524,606 Shelton Oct. 3, 1950 

